I've actually purchased the same kit about a month ago. About two weeks ago I went to go buy some bottle paint for it and ran into the same situation. I don't want spray cans. I just now went to the Tamiya website and clicked on the contact us link and sent them an e-mail:
"I have purchased the A6M2 Zero and the colors to paint it are either AS-21 Dark Green or AS-29 Gray Green. But both of those are spray cans and I haven't seen a corresponding acrylic bottle. Can you tell me if Tamiya make these colors in the little bottles and what the X/XF designation is?"
I used mostly your wording. They say answers can take up to 72 hours. If they respond I'll send you the info.
Goodluck.